Currently, I'm reading "Conquer Your Campus" and Redman says "Compliments are things that should come spontaneously because a girl is awesome in some way."

What?!

I've always learned that compliments should be withheld, something that should happen after f-closes. But he's saying otherwise. So, what compliments are allowed? Genuine compliments? What if it's "You're really pretty," is that okay (a little creepy in my perspective)?

TL:DR: When are compliments allowed!?